The present invention relates to the adjustment of the angular position of a steering wheel on a steering-column shaft of a motor vehicle, and more particularly has as its object a device for the fine adjustment of the relative angular orientation setting of a steering-column shaft and a steering wheel of a motor vehicle, which are joined together by fastening means of the screw and nut type.
It is usual for a steering wheel in a motor vehicle to comprise a rim and a hub, which are joined together in the conventional manner by one or more radial spokes.
The hub is most often metallic and enclosed in a structure usually consisting of plastics material, if necessary equipped with reinforcements.
The setting of the orientation of the steering wheel on a free end of a steering-column shaft is generally effected with the aid of an interengaging connection system consisting of splines which are formed in the steering column and which engage with corresponding complementary splines on the hub.
Torque is generally transmitted from the steering wheel to the shaft by a conical joint comprising a female conical bearing surface on the hub and a male conical bearing surface on the shaft.
The steering wheel is mounted axially on the steering-column shaft with the aid of screw and nut fastening means, for example a self-locking nut which is screwed onto the threaded end of the steering-column shaft and which bears against a washer interposed between this nut and the hub.
The steering wheel is fitted on the steering column after the various adjustments of the front axle assembly of the vehicle have been completed. These adjustments are made after the steering drag link and the steering column associated with it have been placed in position. This has repercussions on the steering column, and the shaft of the latter turns to a greater or lesser extent about its axis.
It will then be realized that in most cases the splines carried by the steering-column shaft will not occupy an angular position enabling the steering wheel to be placed in position with an orientation such that the spokes of the steering wheel will assume an exact position dictated by aesthetic considerations and allowing comfortable driving with, in addition, a clear view of the facia instruments through this steering wheel.
Furthermore, subsequent steering adjustment operations after the steering wheel has been fitted, in the course of servicing or repairs, may displace the orientation of the steering wheel in relation to the original setting.
This original setting is relatively coarse and dependent on the pitch of the splining.
In order to provide a partial remedy for these shortcomings it has been proposed to increase the number of splines. The steering wheel is usually angularly secured on the steering-column shaft by forty splines; the uncertainty of the position of the steering wheel is then 9.degree..
In order to restore the theoretical ideal orientation of the steering wheel, in some cases the adjustment of the front axle assembly of the vehicle is slightly manipulated by acting on the track rods; although this may satisfy aesthetic needs, it cannot fail to impair driving accuracy or to result in dissymetrical tire wear.
To achieve strictly accurate orientation of the steering wheel to a greater extent than the value indicated above, various solutions have been proposed which permit fine adjustment of the relative angular orientation setting of the steering wheel on the steering-column shaft.
Examples of such solutions are the following.
French Patent No. 2 557 992 (corresponding to U.S. Pat. No. 4,624,596) describes a device of this kind. This device comprises essentially a ring or sleeve provided on its inner surface with means for coupling to a steering-column shaft, and on its outer surface with means for coupling to a steering wheel hub. This ring or sleeve is capable of axial translatory movement with the aid of a control member, and at least one of the coupling means is arranged to bring about not only the axial translation of the ring but also an angular displacement of the hub, and therefore of the steering wheel.
French Patent No. 2 592 925 (July 17, 1987) proposes another device of this kind. This device comprises an intermediate sleeve interposed between the shaft and the hub. This sleeve is connected to the shaft with the aid of splines in such a manner as to be capable of axial translatory movement. This sleeve is also connected to the hub with the aid of a screwthread, in such a manner as to be movable, particularly rotatable, in relation to the hub. By acting on the relative angular position of the hub and of this sleeve, which are then locked on the shaft by means of a conical joint, fine adjustment of the orientation of the steering wheel can be achieved.
French Patent No. 2 594 086 (Aug. 14, 1987) describes another device of this type, the construction of which is however much more complex. It also makes use of an intermediate sleeve between shaft and hub, and employs a two-part hub. Use is made of a system of wedges movable axially and relative to one another to act on notches of adjustable size disposed on the front face of the hub and of the sleeve, in order to achieve the fine adjustment of the orientation of the steering wheel.
Although all these devices enable fine adjustment to be achieved, they all have the same disadvantage, particularly because of their relatively complex construction, which accordingly increases the cost of manufacture, assembly and fitting, and even the cost of servicing.